Get a laser. It'll clearly show how good your trigger manipulation is by how the dot moves when the trigger breaks.
If you don't want to use it as a sight, get one of those $10 chinese ones off ebay, they work fine for dry firing. If you want one that can withstand the rigors of shooting, you'll have to pay a lot more more.
Something like this: [ame="https://www.amazon.com/Tworld-Sight-Pistol-P-i-c-t-i-n-n-y/dp/B01G7JW082/ref=sr_1_1?s=sporting-goods&ie=UTF8&qid=1523929035&sr=1-1&keywords=laser+sight"]Amazon.com : Tworld Gun Sight Laser Red Beam Dot Sight Scope for Gun Rifle Pistol P-i-c-a-t-i-n-n-y Mount : Sports & Outdoors[/ame]